Calipers



(No M-odel.)

. H. FOERSTER.

GAMERS. No. 258,225. i Patented May 23,1882.-

N. PETERS Phummhngnphe. washingm n. c,

UNITED STATES PATENT OFFICE.

HENRY FOERSTEB, OF NEWARK, NEW JERSEY.

CALIPERS.

SPECIFICATION forming part of Letters Patent No. 258,225, dated May 23, 1882.`

' Application inea July 2, 1881. (No model.)

To all whom it may concern:

Be it known that 1, HENRY FoERs'rEE, of Newark, in the county of Essex and State of New Jersey, have invented an Improvement in Calipers, Dividers, Ste., ot1 which the follow' ing is a specification.

Figure l is a front view of my improved calipers. Fig. 2 is a central section on the line' c c, Fig. l, on an enlarged scale.

The object of this invention is to improve the character of the pivot in ealipers,dividers, Sto. Heretofore such pivot was a solid pin riveted or headed at both ends. Vheuever a solid pin is thusused it will in the act of riveting be caused to bulge outward more or less and cease to be straight, its longitudinal section obtaining convex surfaces within the body ot' the calipers. This distigurernent ot' the pin produced by the act of riveting injures the calipers, in that it prevents thejaws from moving with the requisite degree ot' freedom. Hence in applying the calipers to use they will have to be jerked into position to match a shaft or other thing to be ineasiired,wliereas theyshould be gently moved from one position to another. .Thejerking action interferes greatly with the necessary exactness and nicety ot' measurement. lt follows that in a good pair ofcalipers it is essential to have thejaws move on their pivots with ease, and yet to prevent them from working too loose on each other. To this end I have substituted for the solid pivotal pin one which is hollow, and which is ot' softer materialthan the material ot'thejaws ofthe calipers. This enables me to keep the outer"sides ofthe hollow pivot always straight. Whatever bulging occurs during the riveting process is inward.

In the accompanying drawings, the letters A and B are the two jaws ofa pair ofealipers. These jaws are of the usual form and construction.

I) and E are the washers, placed against the upper endsof the jaws where they meet.

and l make the pivot F of a softer metal than the jaws, preferring brass or copper whenever the jaws are of iron or steel; but whatever the material of the jaws the pivot should be of a softer metal than they, so that the resistance of the harder metal will prevent the outward bulging of the softer metal during the act ot' riveting. The pivot F is made hollow, as clearly shown, and is placed through the superposed jaws and countersunk washers in the manner in which pivots are usually placed, and is then headed or riveted into position by spreading its ends. During the act ofriveting the metal ofthe pivot, being compressed longitudinally, has a tendency to bulge outward it' the pin be solid, and has on a solid pin no other outlet for the longitudinal compression than the outward bulge; but the tubular pin F,when hammered endwise in the jaws ol' harder metal, instead of bulging outward, will be caused to bulge inward by such hammering, as indicated in Fig. 2, when hammered in riveting, and retain the straight and cylindrical form on the outer side where thejaws ofthe calipers surround il'. i

VlVIy invention is not only applicable to calipers, but also to dividers and analogous instruments.

Lani well aware that it is not new to use eyelets as means of uniting different parts of mechanism, and that tubular eyelets have been. usetlin fans, dividers, and analogous structures. This I do not claim.

What I do claim is- The cali per-jaws A B, combined with the tubular pivot F and eountersunk washers D E, the ends of said pivot being spread substantially as herein shown and described.

HENRY FOERSTER.

Witnesses:

A. v. BEIEsEN, HARRY M. TURK. 

